Mycoplasma cynos is the only species of mycoplasma that has been proven to be associated with the development of respiratory disease in dogs. It was isolated several times from the diseased dogs, mainly those living in kennels. Like other mycoplasmas that inhabit the respiratory system, it is believed that M. cynos is associated with many health complications and that it is often overlooked in clinical treatments. The reason may be in the lack of studies, especially in terms of the relationship between the bacterium and its host cells. Using quantitative PCR, we analysed the influence of M. cynos infection on the expression of genes for cytokines IL-1beta, IL-6, IL-8 and the transcription factor NF-kappaB1 in the immortalised dog cell line DH82. We came to a conclusion that the infection results in a gradual increase in IL-1beta gene expression until 12 h after the infection, in a gradual decrease in IL-6 gene expression until 12 h after the infection, in a gradual increase in IL-8 gene expression until 24 h and then a decrease in 48 h after the infection, and in relatively minor variation of NF-kappaB1 gene expression until 6 h after the infection. M. cynos infection also has an influence on the morphology of DH82 cells, which is manifested in increased vacuolisation 24 h following the infection and in the lysis of individual DH82 cells after 48 h. During this time, an apparent drop in cell viability can also be observed. The viability dropped to 87% after 24 h and to 70% after 48 h after the infection. We also observed a drop in M. cynos concentrations in DH82 cell supernatants in the first 3 h after the infection. We were unable to detect any changes in nitric oxide (NO) concentrations in DH82 cell supernatants, after the infection with M. cynos.